Several processes for forming an artificial multidimensional cyclic or periodic structure having a periodicity substantially equal to that of a wavelength of the light are known. K. Inoue et al., Jpn. J. Appl. Phys. Lett., Vol. 33, L1463 (1994) discloses a process for stretching a round-hole-carrying fiber plate. C. C. Cheng et al., J. Vac. Sci. Technol., B14, 4110 (1996) discloses a process for forming a submicron cyclic structure with respect to GaAs by dry etching. S. Kawakami, Electron. Lett., Vol. 33, No. 14, 1260 (1997) discloses a process for forming a cyclic recessed and projecting pattern on a quartz substrate by the electron beam lithography and dry etching techniques, and thereafter laminating a multilayer film on the resultant substrate by a bias sputtering method provided with a Si target, a SiO2 target and a rotary substrate electrode in the same chamber. On the other hand, a process for applying an Ar excimer laser beam of 126 nm wavelength and an electron line under vacuum to a surface of SiO2 glass, and thereby cutting off a Sixe2x80x94O bond, whereby Si can be formed, is known as a process for generating non-metal ions from glass. However, since the greater part of the excimer laser beam and electron line are absorbed in the surface of the glass, the formation of Si occurs only on the surface thereof, and Si cannot be deposited selectively in the interior of the glass. Therefore, this method does not permit forming a multi-dimensional cyclic structure.
Regarding the formation of an artificial multidimensional cyclic structure, the above-mentioned fiber plate stretching method in which a fiber plate is stretched in one direction permits in principle forming an up to only two-dimensional cyclic structure. In the method using dry etching techniques, there is a limit to an aspect ratio (a ratio of depth to diameter), so that the periodicity of a three-dimensional arrangement is limited. The bias sputtering method permits selecting a structure (shape), and does not have limitations on the periodicity, this method being able to form a three-dimensional cyclic structure. However, a cyclic structure formed by this method is influenced greatly by the shape of a substrate formed by dry etching techniques. Therefore, a uniform cyclic structure can be formed but it is difficult to form structures of a discontinuous cycle, and continuously form cyclic structures of different patterns.
It is an object of the present invention to provide a glass suitable for optical functional elements, which contains a nonmetallic element particle selectively formed in a matrix of the glass.
It is another object of the present invention to provide a process for producing such glass.
According to the present invention, there is provided a glass suitable for optical functional elements. This glass comprises (a) a matrix comprising a compound of at least one nonmetallic element; and (b) a particle selectively formed in said matrix. This particle is made of said at least one nonmetallic element dissociated from said compound by condensing a pulsed laser beam in said matrix.
According to the present invention, there is provided a process for producing a glass suitable for optical functional elements. This process comprises (a) providing a blank glass that is a raw material of said glass, said blank glass comprising a compound of at least one nonmetallic element; (b) condensing a pulsed laser beam to a focal point in said blank glass such that a particle is selectively formed in said blank glass at a position corresponding to said focal point, said particle being made of said at least one nonmetallic element dissociated from said compound; and (c) moving said focal point in said blank glass to produce a pattern of said particle.